Abstract: Processes are described for preparing pure ammonium molybdate from impure roasted molybdenum concentrates. An aqueous solution of nitric acid and ammonium nitrate is contacted with impure molybdenum concentrate to solubilize a major portion of the impurities. The resulting molybdenum concentrate is digested in ammonium hydroxide under conditions that maximize iron precipitation and removal. The resulting ammonium molybdate solution is separated from the sludge and further purified by chelating cation exchange resin in the ammonium form.

Abstract: A spent or scrap tungsten-containing, aluminosilicate catalyst material is blended with a silicate-containing, tungsten-bearing ore concentrate in amounts such that at least about 2.0% by weight of the total tungsten values in the mixture are present in the catalyst material, and then digested with an alkaline solution, e.g., sodium carbonate, under pressure and at an elevated temperature for a period of time sufficient to extract substantially all of the tungsten values from the mixture components. The presence of the catalyst material substantially suppresses the dissolution of silica in the leach liquor.

Abstract: Foaming in the hydrometallurgical treatment of a tungsten-containing aqueous solution due to the presence of carbonaceous organic material impurities, such as flotation reagents, is substantially inhibited by the addition of effective amounts of powdered activated carbon, the carbon with the adsorbed impurities being thereafter separated from the solution by filtering. The activated carbon also protects the solvent extraction circuit from contamination. The method is particularly applicable to slurries of tungsten oxide concentrates during the high temperature, high pressure leaching thereof with sodium carbonate solutions in an autoclave.

Abstract: In the disintegration of a chromite or chromium-containing residue, wherein the chromium-containing material is disintegrated with an alkaline compound in the presence of oxygen and a diluent at a temperature above about 800.degree. C. and thereafter leached, the improvement which comprises pre-roasting the chromium-containing material prior to addition of the alkaline compound. Pre-roasting can be effected at 400.degree. to 1200.degree. C. with addition of certain amounts of silica dioxide and/or aluminum oxide and such additives, depending on the chromium containing material, if still required, are added--prior to disintegration and leaching--in such a quantity to establish a ratio of SiO.sub.2 : AL.sub.2 O.sub.3 of about 2:1 and further a ratio, calculated on the basis of NaOH as the alkaline compound, of SiO.sub.2 : Na.sub.2 O of about 1:0.5 plus a Cr.sub.2 O.sub.3 : Na.sub.2 O ratio of about 1:2 to 1:4.

Abstract: A process is provided for recovering metal values from spent hydrodesulfurization catalyst, the process comprising forming in a pressure reactor an aqueous slurry of finely divided spent catalyst and sodium carbonate, the spent catalyst containing by weight about 2 to 10% Mo, up to about 12% V (e.g., about 2 to 10%), about 0.5 to 4% Co, up to about 10% Ni (e.g., about 0.5 to 5%), occluded oil, coke, sulfide sulfur and the balance essentially alumina. The amount of sodium carbonate employed is at least sufficient under oxidizing conditions to convert molybdenum and any vanadium present to soluble Na.sub.2 MoO.sub.4 and NaVO.sub.3 and to neutralize SO.sub.3 produced during oxidation, the amount of sodium carbonate being at least that required stoichiometrically. The slurry is heated to a temperature of about 200.degree. C. to 350.degree. C. (e.g., 275.degree. C. to 325.degree. C.) and a pressure of about 800 psig to 2500 psig (e.g.

Abstract: Tungsten and molybdenum are recovered from sulfur bearing material such as sulfide sludges by a pollution free process in which the sulfur bearing material is heated with agitation in an aqueous solution of sodium carbonate to form water soluble molybdenum and tungsten compounds without forming any appreciable amount of water soluble sulfur compounds. The reaction mixture is oxidized to convert partially reduced tungsten values or molybdenum values to sodium tungstate and sodium molybdate respectively. The liquid phase containing tungsten and molybdenum is separated from the solid phase containing free sulfur.

Abstract: A process for the removal of arsenic compounds from tungsten and/or molybdenum concentrates by selective extraction, characterized in that the concentrates are extracted with an aqueous solution of a ferric compound of a pH below 2.5 and a temperature of at least 60.degree. C.

Abstract: A process is disclosed wherein tungsten is recovered from hazardous waste material containing said tungsten, arsenic, and other impurities which can consist of magnesium, phosphorus, and silicon and the resulting waste is treated to render it nonhazardous according to EPA standards for arsenic. Said process involves digesting said hazardous waste material in an aqueous solution of an alkali metal hydroxide, adjusting the pH of the resulting solution to about 11.0 to about 13.0 with NaOH to precipitate essentially all of the magnesium and silicon species, filtering the digestion mix to remove the solids from said resulting solution which contains about 80 to about 100% of said tungsten and essentially none of said magnesium and said silicon, slurrying the hazardous solids in hot water, and adding to the slurry a ferric salt solution to precipitate ferric hydroxide, filtering this mixture to give a solid which passes the EPA standard test for solids with respect to arsenic.

Abstract: Ammonium molybdate is produced from molybdenum disulfide concentrate by contacting the concentrate with an aqueous solution of ammonium chloride and chlorine at suitable concentrations and for a sufficient period of time to solubilize molybdenum disulfide present in said concentrate as molybdate ions and form a solution of ammonium molybdate.

Abstract: A hydrometallurgical process is provided for the recovery of molybdenum values from a molybdenum disulfide concentrate containing copper. The process comprises forming an aqueous slurry of finely divided molybdenum concentrate of carbonates and hydroxides of alkali metals, and pressure leaching the slurry in the presence of oxygen at an elevated temperature and pressure for a time sufficient to effect conversion of the contained molybdenum values to alkali metal molybdate and provide a residue containing copper oxide or basic copper carbonate from which copper is later recovered. The molybdenum values are recovered from solution by solvent extraction and the solvent thereafter stripped of the molybdenum as ammonium molybdenum using ammonium hydroxide. The molybdenum is recovered as crystals of ammonium molybdate by crystallization, e.g., by evaporating the stripping solution.

Abstract: In a process for recovering refractory metal values from a refractory metal carbide cemented with a metal binder. The coated cemented carbide is treated with sulfuric acid to deteriorate the coating.

Abstract: A process for the removal of arsenic compounds from tungsten and/or molybdenum concentrates by selective extraction, characterized in that the concentrates are extracted with an aqueous solution of a ferric compound at a pH below 2.5 and a temperature of at least 60.degree. C.

Abstract: Metal constituents are recovered from the heavy bottoms produced during the liquefaction of coal and similar carbonaceous solids in the presence of a catalyst containing a metal capable of forming an acidic oxide by burning the heavy bottoms in a combustion zone at a temperature below the fusion temperature of the ash to convert insoluble metal-containing catalyst residues in the bottoms into soluble metal-containing oxides; contacting the oxidized solids formed in the combustion zone with an aqueous solution of a basic alkali metal salt to extract the soluble metal-containing oxides in the form of soluble alkali metal salts of the metal-containing oxides and recycling the soluble alkali metal salts to the liquefaction zone. In a preferred embodiment of the invention, the bottoms are subjected to partial oxidation, pyrolysis, coking, gasification, extraction or a similar treatment process to recover hydrocarbon liquids and/or gases prior to the burning or combustion step.

Abstract: In a process for recovering refractory metal values from a coated refractory metal carbide cemented with a metal binder, the coated cemented carbide is treated with hydrochloric acid to deteriorate the coating.

Abstract: Synthetic scheelite (calcium tungstate) having a low sulfur content is produced in high yield from an aqueous solution of sodium tungstate, that can be contaminated with sulfate ion dissolved therein, by digesting the solution with solid calcium sulfate whereby low-sulfur calcium tungstate precipitates. The solution remaining after filtration of the calcium tungstate product can be treated with calcium sulfate to precipitate additional purified calcium tungstate or to generate a calcium tungstate-calcium sulfate mixture that can be recycled for digestion with additional sulfate-contaminated sodium tungstate solution.

Abstract: Disclosed is a method of removing uranium from a slurry containing a water-insoluble molybdate and a Group II element, usually calcium. The pH of the slurry is raised with an alkali metal hydroxide and maintained at a level sufficiently high to solubilize insoluble molybdenum compounds. This will generally require a pH of at least 10 which can be achieved by adding sodium hydroxide. Carbonate ion is then added to the slurry in an amount at least sufficient to precipitate the cation of the insoluble molybdenum compound. And finally, the solid portion of a slurry, which now contains calcium carbonate and sodium uranate, is separated from the liquid portion, which contains a soluble molybdenum compound.

Abstract: A process for removing sulfur from sulfide-bearing ores by reacting water vapor with the sulfide-bearing ore forming hydrogen sulfide while simultaneously regenerating water vapor by reacting the hydrogen sulfide with lime. Advantageously, the process occurs in the absence of a net consumption or production of gaseous species so that the process can be carried out in a closed system with respect to the gaseous species. Sulfide-bearing ores which can be treated using the process of this invention include sulfide-bearing ores of molybdenum, zinc, iron, mercury, and copper. Advantageously, the molybdenum oxide so produced from the sulfide-bearing ore of molybdenum can be reacted further with lime and water producing calcium molybdate and hydrogen. The chalcopyrite form of the sulfide-bearing ore of copper produces bornite and magnetite.

Abstract: The residue from a Mo-catalyzed coal liquefaction process is treated to recover the Mo in a form in which the Mo can easily be recycled and reused as a catalyst for coal liquefaction. The process includes intimately mixing the residue with alkali in excess of the stoichiometric amount required for water-soluble molybdate formation, subjecting the mixture to an oxidative roast at about 600.degree. C. to about 800.degree. C. for up to about one hour, leaching the roasted product with water to extract Mo values into solution, and then carrying out a series of steps involving acidifying and ammoniating the solution to form a Mo-bearing precipitate which is recovered and dissolved in aqueous ammonium hydroxide to form a solution which can be applied to coal to catalyze coal liquefaction.

Abstract: A process for the oxidative dissociation of chrome-containing ores comprising agglomerating a mixture of a chrome-containing ore, an alkaline substance and a moist solid residue from a preceding operation as a leaning agent, dissociating the agglomerate and then leaching to form a solution of chromate and a solid residue, and separating said solution from said solid residue still wet with said solution. Advantageously the alkaline substance comprises sodium hydroxide or sodium carbonate, the still wet residue is added in such a quantity that the agglomerates obtained have a moisture content of between about 10 and 15% by weight, and at least about 70% by weight of the agglomerates have a diameter from about 0.1 to 3 mm.

Abstract: Tungsten is recovered from tungsten ore concentrates in the form of sodium tungstate by a basic process in which ground ore is first digested in a sodium hydroxide solution followed by diluting the solution to dissolved sodium tungstate separating the solution from the caustic insoluble sludge and crystallizing soluble sodium tungstate, wherein the present invention permits improved recovery of tungsten from difficult to process ores by the process steps of comminuting said tungsten ore concentrate to a particle size less than about 200 mesh, adding the comminuted ore to an aqueous solution of sodium hydroxide at a temperature from about 10 to about 30 degrees centigrade, dispersing said comminuted ore in the aqueous solution of sodium hydroxide prior to digestion, digesting at a temperature of from about 75.degree. C. to about 150.degree. C.

Abstract: Tungsten is recovered from tungsten ore concentrates in the form of sodium tungstate by a basic process in which ground ore is first digested in a sodium hydroxide solution followed by diluting the solution to dissolve sodium tungstate separating the solution from the caustic insoluble sludge and crystallizing soluble sodium tungstate, wherein the present invention permits improved recovery of tungsten from difficult to process ores by the process steps of comminuting said tungsten ore concentrate to a particle size less than 325 mesh, adding said comminuted ore to aqueous sodium hydroxide at a concentration of at least 10 molar and digesting at a temperature of from about 75.degree. C. to 150.degree. C. for a sufficient period of time to convert substantially all of the tungsten values to soluble sodium tungstate, and diluting the mixture to reduce the sodium hydroxide concentration to between about 4.5 and 5.5 molar at a temperature below about 90.degree. C.

Abstract: Tungsten is recovered from tungsten ore concentrates in the form of sodium tungstate by a basic process in which ground ore is first digested in a sodium hydroxide solution followed by diluting the solution to dissolve sodium tungstate separating the solution from the caustic insoluble sludge and crystallizing soluble sodium tungstate, wherein the present invention permits improved recovery of tungsten from difficult to process ores by the process steps of comminuting said tungsten ore concentrate to a particle size less than about 200 mesh, dispersing the comminuted ore to separate agglomerated particles, adding the dispersed ore to aqueous sodium hydroxide at a concentration of at least 10 molar and digesting at a temperature of from about 75.degree. C. to 150.degree. C. for a sufficient period of time to convert substantially all of the tungsten values to soluble sodium tungstate, and diluting the mixture to reduce the sodium hydroxide concentration to between about 4.5 and 5.

Abstract: Tungsten is recovered from tungsten ore concentrates in the form of sodium tungstate by a basic process in which ground ore is first digested in a sodium hydroxide solution followed by diluting the solution to dissolve sodium tungstate separating the solution from the caustic insoluble sludge and crystallizing soluble sodium tungstate, wherein the present invention permits improved recovery of tungsten from difficult to process ores by the process steps of drying the insoluble sludge portion, comminuting the dried sludge to a particle size less than about 200 mesh, and dissolving said comminuted sludge in 4.5-5.5 molar NaOH to recover substantially all of the tungsten values.

Abstract: A process for the soda ash digestion of scheelite concentrates is provided, the process comprising forming a slurry of a scheelite concentrate in an aqueous sodium carbonate solution and then digesting the slurry in an autoclave at an elevated temperature of at least about 180.degree. C. The concentration of the Na.sub.2 CO.sub.3 solution is substantially inversely correlated to the digestion temperature and substantially directly correlated to the Na.sub.2 CO.sub.3 /WO.sub.3 weight ratio such as to effect the selective dissolution of at least about 95% of the WO.sub.3 in the concentrate and provide a pregnant liquor containing WO.sub.3 while inhibiting substantial dissolution of gangue minerals.

Abstract: A method for producing tungsten compounds low in phophorus. Calcium tungstate is precipitated from a tungstate solution possibly containing phosphate with a calcium compound. The resulting precipitate is reacted with an alkali carbonate solution under pressure of preferably 15 to 25 bar and the solution resulting is separated from the residue containing substantially all of the phosphate. The resulting solution is collected and is suitable for production of tungsten compositions low in phosphorus.

Abstract: Oxide ores or ore concentrates containing organic matter are slurried with water and heated to a temperature of at least about 230.degree. C. under an oxygen partial pressure of at least about 25 psi to oxidize the organic matter. Advantageously, the process in accordance with the present invention can be used in the treatment of tungsten concentrates and can be employed while the tungsten concentrates are being digested with sodium carbonate or sodium hydroxide solutions.

Abstract: An improvement in a cemented carbide is disclosed. Molybdenum, tungsten and carbon are mixed and heated in a nitrogen-containing atmosphere to form a tungsten-molybdenum carbonitride (Mo, W) (C, N) having the structure of tungsten carbide. The molybdenum-tungsten carbonitride is mixed with a binder metal (and, if desired, another hard material) and sintered in a conventional manner to form a dense, substantially pore-free material which is similar in a number of properties to the more expensive tungsten carbide.

Abstract: A process for preparing W, Mo or mixed metal oxides thereof by oxidizing a reduced metal oxide of the formula (NH.sub.m R.sub.4-m).sub.q.sup.+ MO.sub.p where each R is independently C.sub.1 -C.sub.20 aliphatic, C.sub.7 -C.sub.14 araliphatic or C.sub.3 -C.sub.8 cycloaliphatic with the proviso that adjacent R's, together with the nitrogen atom to which they are attached, may form a 5, 6 or 7 membered heterocyclic ring, m is an integer from 0 to 4, q is a number from about 0.001 to 1/3, M is W or Mo and p is a number from 2 to 3 with aqueous hydrogen peroxide. The so-treated reduced metal oxide is isolated and heated in an oxygen containing atmosphere to form metal oxides of the formula MO.sub.p.

Abstract: A process for conditioning a tungsten concentrate containing tungsten as WO.sub.3, sulfur as sulfide, and calcite to fix at least a portion of the sulfur as calcium sulfate by reaction with the calcite, comprises providing a tungsten concentrate having a calcite content such that less than about 15 wt. % calcium sulfate based on the weight of the WO.sub.3 in the concentrate will be formed and heating the concentrate to a temperature of at least about 500.degree. C. in an oxidizing atmosphere to oxidize substantially all the sulfur in the concentrate to provide a conditioned concentrate having a calcium sulfate content less than about 15% based on the weight of the WO.sub.3, whereby the conditioned concentrate can be efficiently leached with alkali metal carbonates or hydroxides and the resulting alkali metal tungstate solution can be effectively treated to recover an ammonium tungstate solution.

Abstract: A continuous process with feedback control is disclosed for the soda ash digestion of tungsten concentrates in which a slurry of the concentrate in an aqueous sodium carbonate solution is digested in an autoclave at a temperature of at least about 180.degree. C. to provide a pregnant solution of WO.sub.3. High dissolution efficiency is maintained during digestion by continuously monitoring the pregnant solution which includes determining the specific gravity and the Na.sub.2 CO.sub.3 concentration of the pregnant liquor from which feedback signals are produced which are used to control the amount of Na.sub.2 CO.sub.3 and H.sub.2 O fed to the slurry in accordance with the digestion conditions predetermined to provide the desired dissolution efficiency.

Abstract: Alloy scrap containing refractory metals such as chromium, molybdenum, tungsten, vanadium, niobium and tantalum and base metals such as nickel, cobalt, copper and iron are treated to partition the refractory metal values from the base metal values without an energy intensive remelting step. The scrap in finely divided form is calcined in the presence of an oxygen containing gas and a member of a certain group of alkali metal salts at a temperature in the range of 800.degree. C. to 1150.degree. C. for 1/4 hour to four hours. This treatment converts the refractory metals to alkali metal molybdates, tungstates, chromates, vanadates, niobates and tantalates and the base metals to oxides. The calcined product may then be water leached to produce a substantially base metal-free liquor rich in refractory metal values. Both the refractory and the base metal values may be subsequently recovered by conventional hydrometallurgical techniques.

Abstract: A process for the soda digestion of mixed wolframite and scheelite concentrates is provided, the process comprising forming a slurry of the mixed wolframite and scheelite concentrates in an aqueous sodium carbonate solution and then digesting the slurry in an autoclave at a temperature of at least about 180.degree. C. During digestion a predetermined amount of sodium hydroxide is added calculated stoichiometrically to react with NaHCO.sub.3 formed as a result of the hydrolysis of FeCO.sub.3 or FeCO.sub.3 and MnCO.sub.3 produced during the digestion of the wolframite and convert it to Na.sub.2 CO.sub.3. The concentration of the Na.sub.2 CO.sub.3 solution is substantially inversely correlated to the digestion temperature and substantially directly correlated to the Na.sub.2 CO.sub.3 /WO.sub.3 weight ratio ranging from about 0.9 to 2 such as to effect dissolution of at least about 95% of the WO.sub.3 in the concentrate and provide a pregnant liquor containing said WO.sub.3.

Abstract: A process for the soda ash digestion of refractory tungsten concentrates is provided, the process comprising forming a slurry of the concentrate in an aqueous solution to which sodium carbonate is added in stages while digesting the slurry in an autoclave at a selected elevated temperature of at least about 180.degree. C. to control the concentration of the sodium carbonate during digestion to provide high extraction yields of the contained WO.sub.3. The total amount of the Na.sub.2 CO.sub.3 added stage-wise to complete the digestion is substantially inversely correlated to the digestion temperature and substantially directly correlated to the Na.sub.2 CO.sub.3 /WO.sub.3 weight ratio such as to effect dissolution of at least about 97%, and generally at least about 98%, of the WO.sub.3 in the concentrate and provide a pregnant liquor containing WO.sub.3, the stage-wise addition of the sodium carbonate being such as to inhibit the dissolution of gangue minerals, such as silica, contained in the concentrate.

Abstract: A process for recovering and recycling chromium from chromium-iron hydroxide sludge for use in cooling tower make up water and plating solution is disclosed. The process comprises separating chromium from the sludge by selectively oxidizing the trivalent chromium precipitate to soluble hexavalent chromium with a strong oxidizing agent such as chlorine gas, in alkaline medium. The hexavalent chromium ions then enter solution and are thereafter separated from the iron hydroxide precipitate as the sludge is dewatered.

Abstract: A calcium tungstate concentrate is produced by slurrying an aqueous sodium tungstate liquor with calcium carbonate at about 130.degree. C. to about 200.degree. C. while providing sufficient carbon dioxide overpressure to convert sodium carbonate in the slurry to sodium bicarbonate, wherein the conversion of sodium tungstate to solid calcium tungstate in the slurry is promoted. The carbon dioxide is then stripped from the slurry, causing the sodium bicarbonate to convert to sodium carbonate, and a calcium tungstate concentrate is filtered from the slurry. The invention is useful in upgrading impure calcium tungstate concentrates.

Abstract: Basic sodium tungstate leach liquor is treated to reduce the concentration dissolved therein of silica, phosphorus and fluorine impurities in a process which comprises providing a small but effective amount of magnesium in the liquor to maximize removal of silica and phosphorus from solution in the liquor while maintaining the liquor temperature between about 60.degree. C. and about 100.degree. C. and the liquor pH between about 9 and about 11, filtering the liquor, adjusting the liquor pH to between about 6 and about 8 and the liquor temperature to between about 20.degree. C. and about 60.degree. C., and then providing a small but effective amount of aluminum hydroxide in the filtered liquor to maximize removal of fluorine from solution in the liquor while maintaining the liquor temperature between about 20.degree. C. and about 60.degree. C. and the liquor pH between about 6 and about 8.

Abstract: Disclosed is a process for recovering chromium, vanadium, molybdenum, and tungsten from secondary resources such as alloy scrap comprising a refractory metal and base metals such as cobalt nickel, iron, and copper. The scrap is calcined with sodium carbonate in air to convert the refractory metal values to MoO.sub.4.sup..dbd., VO.sub.4.sup..tbd., WO.sub.4.sup..dbd., CrO.sub.4.sup..dbd., and the base metals to water insoluble oxides. A leach of the calcined materials produces a pregnant liquor rich in refractory metals which, after separation of the vanadium, molybdenum and tungsten values, is treated with CO, CHOO.sup.-, CH.sub.3 OH, or HCHO to reduce Cr.sup.+6 to Cr.sup.+3. The carbonate and bicarbonate salts produced as a byproduct of the reduction are recycled to the calcination stage.As a result of the V, W, and Mo partition, a mixed solid comprising CaO.multidot.nV.sub.2 O.sub.5, CaMoO.sub.4, and CaWO.sub.4 is produced.

Abstract: Disclosed is a process for recovering chromium, vanadium, molybdenum, and tungsten from secondary resources such as alloy scrap comprising a refractory metal and base metals such as cobalt, nickel, iron, and copper. The scrap is calcined with sodium carbonate in air to convert the refractory metal values to MoO.sub.4.sup.=, VO.sub.4.sup..ident., WO.sub.4.sup.=, and CrO.sub.4.sup.= and the base metals to water insoluble oxides. A leach of the calcined materials produces a pregnant liquor rich in refractory metals which, after separation of the vanadium, molybdenum and tungsten values, is treated with CO, CHOO.sup.- CH.sub.3 OH, or HCHO to reduce Cr.sup.+6 to CR.sup.+3. The carbonate and bicarbonate salts produced as a byproduct of the reduction are recycled to the calcination stage.As a result of the V, W, and Mo partition, a mixed solid comprising CaO.nV.sub.2 O.sub.5, CaMoO.sub.4, and CaWO.sub.4 is produced.

Abstract: Disclosed is a process for recovering chromium, vanadium, molybdenum, and tungsten from secondary resources such as alloy scrap comprising a refractory metal and base metals such as cobalt, nickel, iron, and copper. The scrap is calcined with sodium carbonate in air to convert the refractory metal values to MoO.sub.4.sup.=, VO.sub.4.sup..ident., WO.sub.4.sup.=, and CrO.sub.4.sup.= and the base metals to water insoluble oxides. A leach of the calcined materials produces a pregnant liquor rich in refractory metals which, after separation of the vanadium, molybdenum and tungsten values, is treated with CO, CHOO.sup.-, CH.sub.3 OH, or HCHO to reduce Cr.sup.+6 to Cr.sup.+3. The carbonate and bicarbonate salts produced as a byproduct of the reduction are recycled to the calcination stage.As a result of the V, W, and Mo partition, a mixed solid comprising CaO.nV.sub.2 O.sub.5, CaMoO.sub.4, and CaWO.sub.4 is produced.

Abstract: A process for the recovery of molybdenum values from leach muds of molybdenite concentrates which have been roasted in air to convert molybdenum sulfide to molybdenum trioxide and subsequently leached with an aqueous alkaline solution for the recovery of soluble molybdenum salts. Leach mud is treated by the process of this invention by repulping the leach mud with aqueous ammonium hydroxide under pressure, at a temperature in the range of about 50 to 150.degree. C. for a period of 2 or more hours after which undissolved solid material is separated from the ammoniacal leach solution and repulped with an aqueous caustic leach solution at a temperature in the range of 50.degree. to 150.degree. C. for a period of 2 to 4 hours. Undissolved solid material is separated from the caustic leach solution and both the ammoniacal and the caustic leach solutions processed for the recovery of molybdenum salts therefrom.

Abstract: A process for the oxidizing attack at high temperature of ores containing at least one metal belonging to the group formed by uranium, vanadium and molybdenum, by means of an aqueous liquor containing a majority of sodium bicarbonate and a minority of sodium carbonate according to a ratio by weight of sodium bicarbonate to sodium carbonate of at least 1.5, in the presence of free oxygen injected into the reaction medium, this medium being maintained at a temperature of between 160.degree. C. and 300.degree. C. for at most six hours.

Abstract: In a process for recovering tungsten from cemented tungsten carbide, the cemented tungsten carbide is oxidized to form an oxidized product which is digested in an aqueous solution of an alkali metal hydroxide to form a water soluble alkali metal tungstate portion and an insoluble portion. The improvement of the present invention provides for recovery of tungsten values from the above mentioned insoluble portion by digesting the insoluble portion in an aqueous alkali metal hydroxide solution with a suitable amount of titanium oxide to promote the formation of a soluble alkali metal tungstate.

Abstract: In a process for recovering tungsten from cemented tungsten carbide, the tungsten carbide is oxidized to form an oxidized product and the oxidized product is digested in an aqueous solution of alkali metal hydroxide to form a soluble portion containing tungsten values and an insoluble residue portion. According to the improved process of the present invention, tungsten values are recovered from the insoluble residue portion by mixing the insoluble portion with an alkali metal carbonate to form a resulting mixture, roasting the resulting mixture in an atmosphere containing oxygen to oxidize the insoluble portion and form another product which is leached with water to recover soluble tungsten values.

Abstract: A method for producing alkali metal chromates by a single roast of chrome ores without the use of calcium oxide is disclosed. A double roast embodiment is also contemplated for obtainment of enhanced yields. The pollution and hygiene problems associated with the use of lime are substantially eliminated and only negligible amounts of alumina are found in the product chromate liquors without employing steps previously thought necessary. These advantages are achieved by controlling (1) the Bichromate Equivalent: aluminum oxide ratio in the mix, (2) the amount of alkali metal salts added to the mix, (3) the roasting time, (4) the composition and alkalinity of the liquor used for leaching the roast, and (5) the temperature employed. Recovery of vanadium values from the alkali metal chromate liquors is also disclosed.

Abstract: Method for the recovery of high purity Cr.sub.2 O.sub.3 from a Na.sub.2 CrO.sub.4 or Na.sub.2 Cr.sub.2 O.sub.7 solution by producing (NH.sub.4).sub.2 CrO.sub.4 by solvent extraction, evaporating the aqueous (NH.sub.4).sub.2 CrO.sub.4 and igniting the resulting solids to provide high purity Cr.sub.2 O.sub.3.

Abstract: Molybdenum is recovered from dilute, ammoniacal, molybdenum containing solutions by adding ferrous ions to the solution to precipitate an iron hydroxide-ammonium molybdate complex. The precipitate is separated from the aqueous raffinate and is treated with acid to resolubilize the molybdenum in the complex. Molybdenum values are recovered from the resulting acid solution by ion exchange. The aqueous raffinate is purged of iron and is reused.

Abstract: Molybdenum trioxide containing potassium is heated to a temperature sufficiently high (i.e. at least about 525.degree. C.) to render the potassium soluble in hot water, the heated trioxide is quenched to less than about 400.degree. C. at a rate of at least about 30.degree. C. per minute, the quenched trioxide is leached with hot water (between about 50.degree. C. and about 100.degree. C.) to leach the solubilized potassium and after liquid-solids separation the molybdenum trioxide is dissolved in ammonium hydroxide to form ammonium molybdates, which can be recovered from solution and then can be calcined to chemical grade molybdic oxide. The process is advantageously conducted in conjunction with the roasting of molybdenite.

Abstract: Method for the recovery of chrome hydrate or high purity Cr.sub.2 O.sub.3 from chromium ores by roasting the ore with Na.sub.2 CO.sub.3 and CaO, water leaching the roasted mass, precipitating aluminum impurities from the leach liquor as Al(OH).sub.3 and contacting the leach liquor with sulfur and NaOH in order to reduce the chromium values in the leach liquor from valence 6 to 3 to provide a chrome hydrate precipitate. The chrome hydrate precipitate is acid repulped to provide a chrome hydrate from which sodium impurities have been removed. The chrome hydrate is dried and the resulting solids are calcined to provide a high purity Cr.sub.2 O.sub.3.

Abstract: Tungsten is extracted from hot springs tungsten ores by means of a process comprising (1) calcining the ore, (2) quenching the calcined ore in aqueous alkaline solution and (3) treating the resulting slurry at elevated temperature and pressure to extract the tungsten values from the ore.

Abstract: A method for treating nonferrous metal hydroxide sludge waste to separate and recover the nonferrous metals therein wherein the waste is first mixed with an alkali hydroxide or carbonate, dried, and then roasted and the water-insoluble residue in the roasted material is treated with sulfuric acid to produce an acid-insoluble residue and a sulfuric acid solution containing copper, aluminum and chromium and thereafter, separating the copper from this solution by liquid-liquid extraction and thereafter, separating the aluminium, chromium, zinc and nickel from the remaining solution by separate liquid-liquid extraction steps.